The marketing manager of a company that manufactures and distributes farming equipment (such as combine harvesters, ploughs and tractors) recorded the number of farming units sold quarterly for the period 2008 to 2011.
|
Quarter
|
2008
|
2009
|
2010
|
2011
|
|
Summer
|
57
|
60
|
65
|
64
|
|
Autumn
|
51
|
56
|
60
|
62
|
|
Winter
|
50
|
53
|
58
|
58
|
|
Spring
|
56
|
61
|
68
|
70
|
(a) Find the quarterly seasonal indexes for farming equipment sold.
(b) Do seasonal forces significantly influence the sale of farming equipment? Comment.
(c) Calculate the least squares trendline for the sales of farming equipment.
(d) Prepare seasonally adjusted trend estimates of the number of farming units that this company can expect to sell in each quarter of 2012.
(e) Use Excel to prepare the quarterly seasonal indexes and derive the seasonally adjusted trend estimates as required in (d).